Cylindrical single-piece lithium-ion battery of 400Ah and its preparation method

ABSTRACT

A cylindrical single-piece lithium-ion battery of 400 Ah includes: a cylindrical battery enclosure ( 1 ), a battery mandrel ( 3 ), a plurality of tabs ( 4 ), a wiring terminal ( 6 ), a positive and negative electrode cover ( 11 ); a positive electrode sheet, said battery positive electrode is composed of LiFePO 4 , conductive carbon-black, graphite, adhesive such as PVDF, and solvent such as NMP; a negative electrode sheet, the battery negative electrode is composed of lithium titanate, conductive carbon-black, graphite, adhesive such as PVDF, and solvent such as NMP. The cylindrical lithium-ion battery made by the invention has a capacity of 400 Ah which is the one reportedly having the largest capacity in the world presently.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from PCT Application No.PCT/CN2013/071757, filed Feb. 22, 2013, CN Application No. CN201310048865.0, filed Feb. 7, 2013, and CN Application No. CN201320070958.9, filed Feb. 7, 2013, the contents of which areincorporated herein in the entirety by reference.

FIELD OF THE INVENTION

The present invention relates to a lithium-ion battery and moreparticularly, relates to a cylindrical single-piece lithium-ion batteryof 400 Ah and its preparation method thereof.

BACKGROUND OF THE INVENTION

With time coming into 21th century, and with the development ofscientific and technology and forthcomingness of information society,especially with the widespread promotion of kinds of mobilecommunication devices, electronic equipment, office automation products,domestic appliances and medical devices, people have greater demand onenergy. At the same time, to alleviate conflict of human being withnature and seek for sustainable development, it has become a rigorouschallenge in the 21th century for human to protect nature environmentand nature resources. Therefore, it has been a major subject for variouscountries to develop and exploit new energy and new materials.

Electric energy is very important and indispensable energy for oureveryday life and work. Use of any other resources will rely uponelectric energy. Also, preservation, conversion and transportation ofelectric energy all involve battery technique.

In present information era, people have higher and higher requirementfor power supply performance, in addition to increased requirement foramount of power supply. The requirement mostly includes high powerdensity, high specific energy, long cyclic lifetime, and large capacity.Also, higher requirement has been imposed to power supply in terms ofsafety, cost and environment friendship. Conventional battery such aslead acid battery, Ni—Cd battery and Ni-MH battery suffers fromdrawbacks such as short lifetime, low energy density and environmentpollution, thus greatly limiting their use. As lithium-ion battery bearsgood electrochemical performance, it has become popular new high energygreen battery.

Lithium-ion battery is a new type of battery developed from lithiumbattery. When compared with lithium battery, the most significantadvantage of it lies in: material obtained by lithium ion intercalationand de-intercalation may be used to replace lithium, thus resolvingproblems of lithium anode passivating and dendrite penetration. Inaddition to maintaining high capacity and high voltage of lithiumbattery, charging-discharging efficiency and cycle life of it are alsoimproved significantly. Moreover, the safety of battery is alsoenhanced.

Currently, ordinary material used as anode of lithium-ion batterygenerally includes layered lithium-intercalated compound LiMO₂,spinel-type lithium intercalated compound LiM₂O₄, and olivine-typelithium intercalated compound LiMPO₄.

LiCoO₂ and LiNiO₂ is common layered lithium intercalation compound. Asanode material, LiCoO₂ has high lithium intercalation potential andideally, its capacity can be up to 274 mAh/g. In actual cycle periodhowever, when hale number of lithium ions is extracted, capacity of thematerial will be decreased expressly, thus leading to tendency ofcollapsing of its layered structure. As such, the actual capacity is nomore than 150 mAh/g. Furthermore, resource of Cobalt (Co) is rare,expensive, and has certain toxicity. Therefore, some active materialwith comprehensive electrochemical characteristics, wide availability,and low cost, must be developed to replace Co. Theoretically, LiNiO₂anode material has specific capacity of 275 mAh/g and actually is canget up to 190-210 mAh/g evidently higher than LiCoO₂. Accordingly, it isregarded as one of most prospective anode materials for lithium-ionbattery following LiCoO₂. However, LiNiO₂ has some disadvantageslimiting its application range, such as rapid decrease in cyclecapacity, bad thermal stability and the like.

LiMn₂O₄ Anode material is typical representation of spinel-type lithiumintercalation compound, and its theoretical capacity is 148 mAh/g, andits actual capacity is about 120 mAh/g. Though LiMn₂O₄ has advantages oflow cost, non-toxicity, and good safety, it has unstable latticestructure and capacity attenuation in charging-discharging cycleespecially under high temperature of 55° C., thus hindering itsdevelopment and application.

As a most common lithium-ion battery anode material, olivine-typelithium intercalated LiFePO₄ has a series of advantages including hightheoretical specific capacity (about 170 mAh/g), low cost, goodenvironment friendship, long cycle lifetime, high thermal stability, andsafety. Due to these advantages, it has become hot topic to beresearched and developed in present battery industry, and has beenexpected to be a commercialized lithium battery anode material. As apowerful battery, LiFePO₄ lithium battery will necessarily becomealternative of other types of lithium batteries such as lead acid, Ni-MHand Ni—Cd batteries. Accordingly, LiFePO₄ lithium battery has beenconsidered as a mark of new era of lithium-ion battery.

At present, ordinary LiFePO₄ lithium battery uses graphite as cathodedue to its high specific capacity and low and steady discharging.However, as potential of carbon cathode is close to a standard potentialof lithium, in case of battery overcharging, metal lithium may becrystallized on the surface of the carbon electrode and resulting inshort circuit. Further, majority electrolyte becomes unsteady under thispotential and, the electrolyte is subject to decomposing on theelectrode surface and therefore, causes generation of mixture ofinflammable gases and presents potential safety problem. In addition,insertion of Li+ into the carbon electrode will result in volumedeformation in amount of 10%, causing discontinuity among particles. Itfurther causes loosening and peeling off of the interface between theelectrode and electrolyte and between the electrode andcurrent-collector. These factors urge the researchers to make decorationand modification to the present cathode materials and continuously seekfor novel lithium-ion battery cathode material with good property,simple manufacture process and low cost. Results of nail test made upon100 Ah cylindrical LiFePO₄/C lithium-ion battery show that the batterysurface temperature can reach 200° C. Apparently, regard to largecapacity powerful battery of 100 Ah and above, it is desired to obtainhighly safe and steady cathode material.

Li₄Ti₅O₁₂ is an ideal intercalation of electrode material. Intercalationand de-intercalation of Li+ has little impact on material structure andtherefore, it is called “zero deformation” material. The potential ofLi₄Ti₅O₁₂ relative to the lithium electrode is 1.55V (relative toLi/Li+), the ideal theoretical capacity is 175 mAh/g, and experimentalspecific capacity reaches 150-160 mAh/g. It also has good cycleproperty, long and flat discharging feature, clear voltage rapid changeat the end of charging and discharging period, high intercalationlithium potential without crystallization of lithium, capability ofbeing utilized between stable voltage range of most liquid electrolytes,high Coulombic Efficiency (close to 100%), wide source availability,clean and environment friendly feature. Accordingly, it has featuresrequired by the next generation of lithium-ion battery such as much morecharging repetition times, rapid charging speed and high safety.Comparatively, nail test for 100 Ah cylindrical LiFePO₄/Li₄Ti₅O₁₂lithium-ion battery shows that the battery surface temperature is only40° C. It is clear that the use of Li₄Ti₅O₁₂ as cathode materialimproves safety of large capacity powerful lithium-ion battery andpromotes commercialization of it.

SUMMARY OF THE INVENTIONS

The objection of the present invention is to provide a cylindricallithium-ion battery with super capacity and a simple preparation methodthereof.

A cylindrical single-piece lithium-ion battery of 400 Ah includes:

A cylindrical battery enclosure 1, a battery mandrel 3, a plurality oftabs 4, a wiring terminal 6, a positive and negative electrode cover 11;

Positive electrode sheet: said battery positive electrode is composed ofLiFePO₄, conductive carbon-black, graphite, adhesive such as PVDF, andsolvent such as NMP in weight % of42.0-43.0:1.3-1.7:0.8-1.2:2.5-3.5:51.0-53.0. In addition, aluminum foilis used as current-collector;

Negative electrode sheet: the battery negative electrode is composed oflithium titanate, conductive carbon-black, graphite, adhesive such asPVDF, and solvent such as NMP in weight % of49.0-50.0:0.8-1.2:0.8-1.2:3.0-4.0:44.0-46.0. In addition, aluminum foilis used as current-collector.

As a preferable solution, the wiring terminal is fixedly connected withthe battery mandrel axially and further includes:

A supporting bracket 5, a sliding ring 7, a tab clamping nut 8, aninsulation cushion 9, an O-shaped ring 10, a wiring terminal clampingnut 12 and a locating screw 13.

The aluminum foil has a thickness of 30±2 μm, and width of 320±1 mm. Thelength of the positive and negative electrode sheets both have a lengthof 33.81 m.

The tab has a length of 70±1 mm, width of 10±0.1 mm, and thickness of0.15±0.015 mm.

Three safety valve sheets are provided on each of positive and negativeelectrode sheets.

Each valve sheet has a diameter of 13 mm, thickness of 0.5 mm, and burstpressure of 7.5-8 kg.

The cylindrical battery enclosure 1 and electrode cover 11 are all madeof stainless steel, and have a diameter of 134 mm, length of 450 mm, andwall thickness of 1 mm.

A method of making said cylindrical single-piece lithium-ion battery of400 Ah is described as follows.

(1) Preparation of Electrodes

Pre-baked crude materials including LiFePO₄, conductive carbon black,graphite, adhesive PVDF, and solvent NMP in weight % of42.0-43.0:1.3-1.7:0.8-1.2:2.5-3.5:51.0-53.0 are evenly mixed together toform battery positive electrode slurry; Pre-baked crude materialsincluding lithium titanate, conductive carbon black, graphite, adhesivePVDF, and solvent NMP in weight % of49.0-50.0:0.8-1.2:0.8-1.2:3.0-4.0:44.0-46.0 are evenly mixed together toform battery negative electrode slurry;

During coating and rolling process, both of the positive and negativeelectrodes use aluminum foil as the current-collector. The aluminum foilhas a thickness of 30±2 μm, and width of 320±1 mm; the length of bothpositive and negative electrode sheets is 33.81 m.

(2) Assembly of the Battery

The electrode sheets obtained from above steps are heated for 48 h at atemperature of 100° C.; Then the positive and negative electrode sheetsare placed to be aligned with and parallel with a membrane and areloaded into a full automatic winding machine; next, one hundred ofaluminum tabs are welded onto an aluminum foil edge of each positive andnegative electrode sheets, and high-temperature resistant adhesive paperis employed to secure firmly a root portion of the tabs. Each aluminumtab of positive and negative electrode sheets has a length of 70±1 mm,width of 10±0.1 mm and thickness of 0.15±0.015 mm;

The plurality of evenly divided positive and negative tabs 4 passthrough a space defined between the wiring terminal 6 and sliding ring7, and then are locked by the tab clamping nut 8 (this connection manneris called “wiring collar”); a cell pack is carefully inserted into theenclosure 1; each of two ends of the enclosure 1 is wrapped by asupporting bracket 5; after finishing of the bracket 5, the wiringterminal 6, O-shaped ring 10, insulation cushion 9 and cover 11 areassembled together in sequence and are clamped together by the clampingnut 12 and locating screw 13; three safety valve sheets are provided oneach of positive and negative electrode covers. Each valve sheet has adiameter of 13 mm, thickness of 0.5 mm, and burst pressure of 7.5-8 kg;during winding, assembling and welding procedure, a multimeter is usedto detect short circuit. When doing so, vacuum injecting means is usedto perform electrolyte injection. Said electrolyte may be LiPF₆(EC+PC+DMC+DEC). Finally, a laser welder runs to weld covers to two endsof the battery in a sealing manner.

Compared to prior art, the present invention has the followingadvantages.

(1) The cylindrical lithium-ion battery made by the invention has acapacity of 400 Ah which is the one reportedly having the largestcapacity in the world presently.(2) The invention utilizes unique matched positive and negative slurryingredient configuration and leading preparation technology. In thepresent invention, it is the first time to use LiFePO₄ with good thermalstability as positive electrode material, and use “zero deformation”material for example lithium titanate as negative electrode material.The cycle lifetime of the battery is at least 8000 times (and in theory,it can be up to 20000 times). This cycle lifetime is about 2-4 timeslonger than those lithium-ion batteries in the present marketplace. Assuch, the safety and cycle lifetime of the battery is improveddramatically.(3) Nail test applied to the cylindrical lithium-ion battery made by theinvention indicates that the battery never burns or bursts. The surfacetemperature of the battery is only 34° C. Comparatively, nail testapplied to a conventional LiFePO₄/C battery seen in the marketplacedemonstrates that the surface temperature of the battery is 200° C.Accordingly, the present invention enhances the battery safety.(4) In the present invention, novel cylindrical configuration is used,which has utility, anti-erosion, pressure resistance, anti-impact, shockresistance, low cost, large electrical capacity and has reasonableinternal construction, thus greatly improving heat dissipation, thermalreliability and safety.

(5) Both of positive and negative current-collector use aluminum foils;tabs are made of aluminum material. Compared to current-collector andtabs made of copper in the marketplace, the invention shows significantcost reduction.

(6) In a preferred embodiment, 3 safety valves are installed on bothends of the covers; unique “wiring collar construction” is applied toconnect the cell pack and wiring terminals. These designs reduceinternal resistance of the battery dramatically and improve safety ofthe battery.

(7) The invention has simple preparation process and is suitable toindustrialized production.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing assembling of a cylindricalsingle-piece LiFePO₄/Li₄Ti₅O₁₂ lithium-ion battery of 400 Ah madeaccording to a first embodiment. In this figure, 1 is cylindricalbattery enclosure 1, 2 is battery winding core, 3 is battery mandrel, 4is tab, 5 is supporting bracket, 6 is wiring terminal, 7 is slidingring, 8 is clamping nut, 9 is insulation cushion, 10 is O-shaped ring,11 is positive and negative cover, 12 is wiring terminal clamping nut,and 13 is locating pin.

FIG. 2 is a photo of a cylindrical single-piece LiFePO₄/Li₄Ti₅O₁₂lithium-ion battery of 400 Ah made in the first embodiment.

FIG. 3 shows design sizes in mm of a cylindrical single-pieceLiFePO₄/Li₄Ti₅O₁₂ lithium-ion battery of 400 Ah made in the firstembodiment.

FIG. 4 is a charging-discharging curve of a cylindrical single-pieceLiFePO₄/Li₄Ti₅O₁₂ lithium-ion battery of 400 Ah made in the firstembodiment, wherein the x-axis denotes capacity in unit of Ah, while theY-axis denotes voltage in unit of volt.

FIG. 5 shows a photo of a cylindrical single-piece LiFePO₄/Li₄Ti₅O₁₂lithium-ion battery of 400 Ah made in the first embodiment beforeapplication of a nail test.

FIG. 6 shows a photo of a cylindrical single-piece LiFePO₄/Li₄Ti₅O₁₂lithium-ion battery of 400 Ah made in the first embodiment afterapplication of a nail test.

FIG. 7 shows a photo illustrating burning and explosion of 20 AhLiCoO₂/C lithium-ion battery after application of nail test.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS OF THE INVENTION

Reference is now made to the accompanying drawings in which is shown anillustrative embodiment of the present invention from which its featuresand advantages will be apparent.

Embodiment 1

Pre-baked crude materials including LiFePO₄, conductive carbon black,graphite, adhesive PVDF, and solvent NMP in weight % of42.0-43.0:1.3-1.7:0.8-1.2:2.5-3.5:51.0-53.0 and in total weight of 7.279kg are evenly mixed together to form battery positive electrode slurry;

Pre-baked crude materials including lithium titanate, conductive carbonblack, graphite, adhesive PVDF, and solvent NMP in weight % of49.0-50.0:0.8-1.2:0.8-1.2:3.0-4.0:44.0-46.0 and in total weight of 6.656kg are evenly mixed together to form battery negative electrode slurry.

During coating and rolling process, both of the positive and negativeelectrodes use aluminum foil as the current-collector. The aluminum foilhas a thickness of 30±2 μm, and width of 320±1 mm; the length of bothpositive and negative electrode sheets is 33.81 m.

The electrode sheets obtained from above steps are heated for 48 h at atemperature of 100° C.; Then the positive and negative electrode sheetsare placed to be aligned with and parallel with a membrane and areloaded into a full automatic winding machine; next, one hundred ofaluminum tabs are welded onto an aluminum foil edge of each positive andnegative electrode sheets, and high-temperature resistant adhesive paperis employed to secure firmly a root portion of the tabs. Each aluminumtab of positive and negative electrode sheets has a length of 70±1 mm,width of 10±0.1 mm and thickness of 0.15±0.015 mm.

The plurality of evenly divided positive and negative tabs 4 passthrough a space defined between the wiring terminal 6 and sliding ring7, and then are locked by the tab clamping nut 8 (this connection manneris called “wiring collar”); a cell pack is carefully inserted into theenclosure 1; each of two ends of the enclosure 1 is wrapped by asupporting bracket 5; after finishing of the bracket 5, the wiringterminal 6, O-shaped ring 10, insulation cushion 9 and cover 11 areassembled together in sequence and are clamped together by the clampingnut 12 and locating screw 13 (See for FIG. 1); three safety valve sheetsare provided on each of positive and negative electrode covers. Eachvalve sheet has a diameter of 13 mm, thickness of 0.5 mm, and burstpressure of 7.5-8 kg; during winding, assembling and welding procedure,a multimeter is used to detect short circuit. When doing so, vacuuminjecting means is used to perform electrolyte injection. Saidelectrolyte may be LiPF₆ (EC+PC+DMC+DEC). Finally, a laser welder runsto weld covers to two ends of the battery in a sealing manner.

Various parameters are listed below:

Battery enclosure: made of stainless steel, diameter: 134 mm, length:450 mm, weight: 12 Kg; rated capacity: 400 Ah; rated working voltage:1.8V; internal resistance: 0.33 m Ω; cycle lifetime: more than 8000times.

Photos of the cylindrical single-piece LiFePO₄/Li₄Ti₅O₁₂ lithium-ionbattery of 400 Ah made in the first embodiment are shown in FIG. 2, andits contour sizes are indicated in FIG. 3.

The cylindrical single-piece LiFePO₄/Li₄Ti₅O₁₂ lithium-ion battery of400 Ah made in the first embodiment is tested by charging-dischargingwith constant current using battery test equipment such as modelBTS-5V200A produced by Shenzhen New Wale electronic products INC.. Theabove test is conducted according to “Electric automobile lithium-ionbattery” set forth in Chinese automobile industry standard QC/T743-2006.During charging period, current is at first kept constant and thenvoltage is kept constant. The charging restriction voltage is 2.3V.During discharging period, current is constant, and discharging cutoffvoltage is 0.5V. Current with magnitude of 0.33 C is used to perform theabove test.

The cylindrical single-piece LiFePO₄/Li₄Ti₅O₁₂ lithium-ion battery of400 Ah made in the first embodiment has a weight of 12 kg, dischargingcapacity of 417.718 Ah, charging-discharging efficiency of 99.6%,internal resistance of 0.33 mΩ, and cycle lifetime of at least 8000times (in theory, it can be 20000 times).

It is clear from FIG. 4 that the battery has stable charging-dischargingvoltage, long holding time of potential (capacity may be 95% of thedischarging capacity), these being brought by reaction betweenSpinel-type Li₄Ti₅O₁₂ and Rock Salt-type Li₇Ti₅O₁₂. Reaction of the twosubstance makes the electrode potential stable. When above reaction isfinished substantially, the potential will rapidly rise or drop. Whencharging and discharging ends, the resulting significant voltage steepchange may be used to indicate termination of charging and discharging,thereby facilitating detection of the battery capacity.

The cylindrical single-piece LiFePO₄/Li₄Ti₅O₁₂ lithium-ion battery of400 Ah made in the first embodiment has an internal resistance of only0.33 mΩ meaning very good conductivity. The battery electrode sheet oflarge capacity also has great cross-section area and therefore, theinternal resistance of the battery is very small (the resistance is inreverse proportion to the cross-section area). Compared with the batteryprepared using laminated sheets, during winding process of the batteryelectrode sheet, the positive and negative electrode sheets of thebattery prepared by using this technique will be pressed tightly againstthe membrane under the tension. Accordingly, the winding core is robustand has large cross section area. Therefore, the battery has very smallinternal resistance.

In test range of the first embodiment, the capacity of the cylindricalsingle-piece LiFePO₄/Li₄Ti₅O₁₂ lithium-ion battery is not seenattenuated. It is predicted based on feature of Li₄Ti₅O₁₂ and previousdata of battery with small capacity that the cylindrical single-pieceLiFePO₄/Li₄Ti₅O₁₂ lithium-ion battery of 400 Ah will have a cyclelifetime of at least 8000 times (in theory, it can be 20000 times). Thiscycle lifetime is about 2-4 times longer than those lithium-ionbatteries in the marketplace.

The internal resistance, cycle lifetime and other major technicalparameters of the cylindrical single-piece LiFePO₄/Li₄Ti₅O₁₂ lithium-ionbattery of 400 Ah made in the first embodiment have met expected designrequirements.

The cylindrical single-piece LiFePO₄/Li₄Ti₅O₁₂ lithium-ion battery of400 Ah made in the first embodiment is tested by charging-dischargingwith constant current using battery test equipment such as modelBTS-5V200A produced by Shenzhen New Wale electronic products INC.. Theabove test is conducted according to “Electric automobile lithium-ionbattery” set forth in Chinese automobile industry standard QC/T743-2006.Neither burning nor burst has occurred when applying the nail test. Inaddition, 6 safety valves mounted on both covers located at two ends ofthe battery are not opened at all (See FIG. 5). The surface temperatureof the battery is only 34° C. Comparatively, nail test applied to aconventional LiFePO₄/C battery seen in the marketplace demonstrates thatthe surface temperature of the battery is 200° C. Apparently, the safetyof the battery is significantly improved.

Comparative Example 1

Pre-baked crude materials including LiFePO₄, conductive carbon black,graphite, adhesive PVDF, and solvent NMP in weight % of38.0-39.0:0.8-1.2:0.3-0.7:2.5-3.5:56.0-58.0 and in total weight of 2.672kg are evenly mixed together to form battery positive electrode slurry.

Pre-baked crude materials including artificial graphite, conductivecarbon black, adhesive PVDF, and solvent NMP in weight % of36.0-37.0:0.8-1.2:3.0-4.0:58.0-60.0 and in total weight of 1.192 kg areevenly mixed together to form battery negative electrode slurry.

During coating and rolling process, the positive electrode uses aluminumfoil as the current-collector, while the negative electrode uses copperfoil as its current-collector. The aluminum foil has a thickness of 30±2μm, and width of 320±1 mm; and the copper foil has a thickness of 22±2μm, and width of 320±1 mm. The length of both positive and negativeelectrode sheets is 11.00 m.

The electrode sheets obtained from above steps are heated for 48 h at atemperature of 100° C.; Then the positive and negative electrode sheetsare placed to be aligned with and parallel with a membrane and areloaded into a full automatic winding machine; next, 73 aluminum tabs arewelded onto a foil edge of the positive electrode sheet, and 73 coppertabs are welded onto a foil edge of the negative electrode sheet. Thealuminum tab of positive electrode sheet has a length of 70±1 mm, widthof 10±0.1 mm and thickness of 0.1±0.01 mm. The copper tab of negativeelectrode sheet has a length of 70±1 mm, width of 10±0.05 mm andthickness of 0.05±0.01 mm.

The positive and negative tabs are secured onto the corresponding wiringterminals using tab bolts and tab plates. The tabs should be clampedtightly. A cell pack is carefully inserted into a battery casing; eachof two ends of the casing is wrapped by a supporting bracket; afterfinishing of the bracket, the positive and negative wiring terminals,internal insulation rings, O-shaped ring, cover, external insulationring, and wiring terminal anti-loosening cushion are assembled togetherin sequence and are clamped together by the clamping nut; a safety valvesheet is provided on each of positive and negative electrode covers.Each valve sheet has a diameter of 13 mm, thickness of 0.5 mm, and burstpressure of 7.5-8 kg; during winding, assembling and welding procedure,a multimeter is used to detect short circuit. When doing so, vacuuminjecting means is used to perform electrolyte injection. Saidelectrolyte may be LiPF₆ (EC+PC+DMC+DEC). Finally, a laser welder runsto weld covers to two ends of the battery in a sealing manner.

The cylindrical LiFePO₄/C(artificial graphite) lithium-ion battery of100 Ah made in the comparative example 1 is tested bycharging-discharging with constant current using battery test equipmentsuch as model BTS-5V200A produced by Shenzhen New Wale electronicproducts INC.. The above test is conducted according to “Electricautomobile lithium-ion battery” set forth in Chinese automobile industrystandard QC/T743-2006. During charging period, current is at first keptconstant and then voltage is kept constant. The charging restrictionvoltage is 2.0V. During discharging period, current is constant, anddischarging cutoff voltage is 2.0V. Current with magnitude of 0.33 C isused to perform the above test.

The cylindrical LiFePO₄/C(artificial graphite) lithium-ion battery of100 Ah made in the comparative example 1 has a weight of 3.7 kg,discharging capacity of 102.245 Ah, charging-discharging efficiency of93.9%, internal resistance of 0.60 mΩ, and cycle lifetime of about 3000times.

The nail test is conducted according to “Electric automobile lithium-ionbattery” set forth in Chinese automobile industry standard QC/T743-2006to the cylindrical LiFePO₄/C(artificial graphite) lithium-ion battery of100 Ah made in the comparative example 1. Neither burning nor burst hasoccurred. In addition, one of two safety valves mounted on both coverslocated at two ends of the battery is opened. The surface temperature ofthe battery is 200° C.

Comparative Example 2

Pre-baked crude materials including LiFePO₄, conductive carbon black,graphite, adhesive PVDF, and solvent NMP in weight % of38.0-39.0:0.8-1.2:0.3-0.7:2.5-3.5:56.0-58.0 and in total weight of 2.672kg are evenly mixed together to form battery positive electrode slurry.

Pre-baked crude materials including carbon fiber ball, conductive carbonblack, adhesive PVDF, and solvent NMP in weight % of36.0-37.0:0.8-1.2:3.0-4.0:58.0-60.0 and in total weight of 1.192 kg areevenly mixed together to form battery negative electrode slurry.

During coating and rolling process, the positive electrode uses aluminumfoil as the current-collector, while the negative electrode uses copperfoil as its current-collector. The aluminum foil has a thickness of 30±2μm, and width of 320±1 mm; and the copper foil has a thickness of 22±2μm, and width of 320±1 mm. The length of both positive and negativeelectrode sheets is 11.00 m.

The electrode sheets obtained from above steps are heated for 48 h at atemperature of 100° C.; Then the positive and negative electrode sheetsare placed to be aligned with and parallel with a membrane and areloaded into a full automatic winding machine; next, 73 aluminum tabs arewelded onto a foil edge of the positive electrode sheet, and 73 coppertabs are welded onto a foil edge of the negative electrode sheet. Inaddition, high-temperature resistant adhesive paper is used to attachthe tabs tightly. The aluminum tab of positive electrode sheet has alength of 70±1 mm, width of 10±0.1 mm and thickness of 0.1±0.01 mm. Thecopper tab of negative electrode sheet has a length of 70±1 mm, width of10±0.05 mm and thickness of 0.05±0.01 mm.

The positive and negative tabs are secured onto the corresponding wiringterminals using tab bolts and tab plates. The tabs should be clampedtightly. A cell pack is carefully inserted into a battery casing; eachof two ends of the casing is wrapped by a supporting bracket; afterfinishing of the bracket, the positive and negative wiring terminals,internal insulation rings, O-shaped ring, cover, external insulationring, and wiring terminal anti-loosening cushion are assembled togetherin sequence and are clamped together by the clamping nut; a safety valvesheet is provided on each of positive and negative electrode covers.Each valve sheet has a diameter of 13 mm, thickness of 0.5 mm, and burstpressure of 7.5-8 kg; during winding, assembling and welding procedure,a multimeter is used to detect short circuit. When doing so, vacuuminjecting means is used to perform electrolyte injection. Saidelectrolyte may be LiPF₆ (EC+PC+DMC+DEC). Finally, a laser welder runsto weld covers to two ends of the battery in a sealing manner.

The cylindrical LiFePO₄/C(carbon fiber ball) lithium-ion battery of 100Ah made in the comparative example 2 is tested by charging-dischargingwith constant current using battery test equipment such as modelBTS-5V200A produced by Shenzhen New Wale electronic products INC.. Theabove test is conducted according to “Electric automobile lithium-ionbattery” set forth in Chinese automobile industry standard QC/T743-2006.During charging period, current is at first kept constant and thenvoltage is kept constant. The charging restriction voltage is 3.8V.During discharging period, current is constant, and discharging cutoffvoltage is 2.0V. Current with magnitude of 0.33 C is used to perform theabove test.

The cylindrical LiFePO₄/C(carbon fiber ball) lithium-ion battery of 100Ah made in the comparative example 2 has a weight of 3.7 kg, dischargingcapacity of 104.662 Ah, charging-discharging efficiency of 95.2%,internal resistance of 0.50 mΩ, and cycle lifetime of about 3000 times.

The nail test is conducted according to “Electric automobile lithium-ionbattery” set forth in Chinese automobile industry standard QC/T743-2006to the cylindrical LiFePO₄/C(carbon fiber ball) lithium-ion battery of100 Ah made in the comparative example 2. Neither burning nor burst hasoccurred. In addition, neither of two safety valves mounted on bothcovers located at two ends of the battery is opened. The surfacetemperature of the battery is 180° C.

Comparative Example 3

Pre-baked crude materials including LiCoO₂, conductive carbon black,graphite, adhesive PVDF, and solvent NMP in weight % of39.0-40.0:0.3-0.7:0.8-1.2:1.5-2.5:56.0-58.0 and in total weight of 0.467kg are evenly mixed together to form battery positive electrode slurry.

Pre-baked crude materials including graphite, conductive carbon black,adhesive PVDF, and solvent NMP in weight % of37.0-38.0:0.8-1.2:2.0-3.0:58.0-60.0 and in total weight of 0.261 kg areevenly mixed together to form battery negative electrode slurry.

During coating and rolling process, the positive electrode uses aluminumfoil as the current-collector, while the negative electrode uses copperfoil as its current-collector. The aluminum foil has a thickness of 20±2μm, and width of 183±1 mm; and the copper foil has a thickness of 12±2μm, and width of 183±1 mm. The length of both positive and negativeelectrode sheets is 2.13 m.

The electrode sheets obtained from above steps are heated for 48 h at atemperature of 100° C.; Then the positive and negative electrode sheetsare placed to be aligned with and parallel with a membrane and areloaded into a full automatic winding machine; next, 6 aluminum tabs arewelded onto a foil edge of the positive electrode sheet, and 6 Ni tabsare welded onto a foil edge of the negative electrode sheet. Inaddition, high-temperature resistant adhesive paper is used to attachthe tabs tightly. The aluminum tab of positive electrode sheet has alength of 70±1 mm, width of 10±0.1 mm and thickness of 0.1±0.01 mm. TheNi tab of negative electrode sheet has a length of 70±1 mm, width of10±0.05 mm and thickness of 0.1±0.01 mm.

The positive tab passes through a hole defined in the insulation sheetand then is wrapped with the supporting bracket. Finally, it is weldeddirectly on the inner side of the positive electrode cover (tabletcover). Next, a cell pack is carefully inserted into a batteryenclosure. After that, the negative tab passes through a hole defined inthe insulation sheet and then is welded to the positive tab and finallyis wrapped with the supporting bracket. The O-shaped ring, negativecover, and negative wiring terminal are assembled together tightly insequence; a safety valve sheet is provided on the negative electrodecover. The valve sheet has a diameter of 13 mm, thickness of 0.5 mm, andburst pressure of 7.5-8 kg; during winding, assembling and weldingprocedure, a multimeter is used to detect short circuit. When doing so,vacuum injecting means is used to perform electrolyte injection. Saidelectrolyte may be LiPF₆ (EC+PC+DMC+DEC). Finally, a laser welder runsto weld covers to two ends of the battery in a sealing manner.

The cylindrical LiCoO₂/C lithium-ion battery of 20 Ah made in thecomparative example 3 is tested by charging-discharging with constantcurrent using battery test equipment such as model BTS-5V200A producedby Shenzhen New Wale electronic products INC.. The above test isconducted according to “Electric automobile lithium-ion battery” setforth in Chinese automobile industry standard QC/T743-2006. Duringcharging period, current is at first kept constant and then voltage iskept constant. The charging restriction voltage is 4.2V. Duringdischarging period, current is constant, and discharging cutoff voltageis 3.0V. Current with magnitude of 0.33 C is used to perform the abovetest.

The cylindrical LiCoO₂/Clithium-ion battery of 20 Ah made in thecomparative example 3 has a weight of 0.58 kg, discharging capacity of20.392 Ah, charging-discharging efficiency of 87.1%, internal resistanceof 4.77 mΩ, and cycle lifetime of about 2500 times.

The nail test is conducted according to “Electric automobile lithium-ionbattery” set forth in Chinese automobile industry standard QC/T743-2006to the cylindrical LiCoO₂/Clithium-ion battery of 20 Ah made in thecomparative example 3. The cover of the negative electrode and thesafety valve sheet thereon are both opened. Burning and burst occur tothe battery, as shown in FIG. 7.

Comparative Example 4

Pre-baked crude materials including LiFePO₄, conductive carbon black,graphite, adhesive PVDF, and solvent NMP in weight % of42.0-43.0:1.3-1.7:0.8-1.2:2.5-3.5:51.0-53.0 and in total weight of 3.795are evenly mixed together to form battery positive electrode slurry.

Pre-baked crude materials including lithium titanate, conductive carbonblack, graphite, adhesive PVDF, and solvent NMP in weight % of49.0-50.0:0.8-1.2:0.8-1.2:3.0-4.0:44.0-46.0 and in total weight of 3.472kg are evenly mixed together to form battery negative electrode slurry.

During coating and rolling process, both of the positive and negativeelectrodes use aluminum foil as the current-collector. The aluminum foilhas a thickness of 30±2 μm, and width of 320±1 mm; the length of bothpositive and negative electrode sheets is 17.63 m.

The electrode sheets obtained from above steps are heated for 48 h at atemperature of 100° C.; Then the positive and negative electrode sheetsare placed to be aligned with and parallel with a membrane and areloaded into a full automatic winding machine; next, 60 aluminum tabs arewelded onto an aluminum foil edge of each positive and negativeelectrode sheets, and high-temperature resistant adhesive paper isemployed to secure firmly a root portion of the tabs. Each aluminum tabof positive and negative electrode sheets has a length of 70±1 mm, widthof 10±0.1 mm and thickness of 0.15±0.015 mm.

The plurality of evenly-divided positive and negative tabs pass througha space defined between the wiring terminal and sliding ring, and thenare locked by the tab clamping nut (this connection manner is called“wiring collar”); a cell pack is carefully inserted into the enclosure;each of two ends of the enclosure is wrapped by a supporting bracket;after finishing of the bracket, the positive and negative wiringterminals, O-shaped ring, insulation cushion and cover are assembledtogether in sequence and are clamped together by the clamping nut andlocating screw; two safety valve sheets are provided on each of positiveand negative electrode sheets. Each valve sheet has a diameter of 13 mm,thickness of 0.5 mm, and burst pressure of 7.5-8 kg; during winding,assembling and welding procedure, a multimeter is used to detect shortcircuit. When doing so, vacuum injecting means is used to performelectrolyte injection. Said electrolyte may be LiPF₆ (EC+PC+DMC+DEC).Finally, a laser welder runs to weld covers to two ends of the batteryin a sealing manner.

The cylindrical LiFePO₄/Li₄Ti₅O₁₂ lithium-ion battery of 200 Ah made inthe example 4 is tested by charging-discharging with constant currentusing battery test equipment such as model BTS-5V200A produced byShenzhen New Wale electronic products INC.. The above test is conductedaccording to “Electric automobile lithium-ion battery” set forth inChinese automobile industry standard QC/T743-2006. During chargingperiod, current is at first kept constant and then voltage is keptconstant. The charging restriction voltage is 2.3V. During dischargingperiod, current is constant, and discharging cutoff voltage is 0.5V.Current with magnitude of 0.33 C is used to perform the above test.

The cylindrical LiFePO₄/Li₄Ti₅O₁₂ lithium-ion battery of 200 Ah made inthe example 4 has a weight of 7 kg, discharging capacity of 204.754 Ah,charging-discharging efficiency of 98.9%, internal resistance of 0.47mΩ, and cycle lifetime of at least 8000 times (in theory, it can be20000 times).

The cylindrical LiFePO₄/Li₄Ti₅O₁₂ lithium-ion battery of 200 Ah made inthe example 4 is tested by charging-discharging with constant currentusing battery test equipment such as model BTS-5V200A produced byShenzhen New Wale electronic products INC.. The above test is conductedaccording to “Electric automobile lithium-ion battery” set forth inChinese automobile industry standard QC/T743-2006. Neither burning norburst has occurred during the nail test. In addition, 4 safety valvesmounted on both covers located at two ends of the battery are not openedat all. The surface temperature of the battery is 34° C.

In a summary, the cylindrical LiFePO₄/Li₄Ti₅O₁₂ lithium-ion battery madeby the first embodiment of the invention has large capacity, smallinternal resistance, long cycle lifetime, good safety reliability,strong environment adaptation, good uniformity and accordingly, it canbe applied widely to electric automobile, hybrid power automobile,military equipment, aerospace, hydraulic power, thermal power, windpower, polar power station system and uninterrupted power supply forpost telecommunications, thus meeting increasing marketplacerequirements, and having wide prospect.

It is the definite choice for developing and utilizing green energy. Thecylindrical lithium-ion battery with high capacity, large power and goodsafety will find its great application and prospect throughout theworld.

1. A cylindrical single-piece lithium-ion battery of 400 Ah comprising:a cylindrical battery enclosure (1), a battery mandrel (3), a pluralityof tabs (4), a wiring terminal (6), a positive and negative electrodecover (11); a positive electrode sheet: said positive electrode sheet iscomposed of LiFePO4, conductive carbon-black, graphite, adhesive such asPVDF, and solvent such as NMP n weight % of42.0-43.0:1.3-1.7:0.8-1.2:2.5-3.5:51.0-53.0; in addition, aluminum foilis used as current-collector; a negative electrode sheet: the negativeelectrode sheet is composed of lithium titanate, conductivecarbon-black, graphite, adhesive such as PVDF, and solvent such as NMPin weight % of 49.0-50.0:0.8-1.2:0.8-1.2:3.0-4.0:44.0-46.0; in addition,aluminum foil is used as current-collector; a supporting bracket (5), asliding ring (7), a tab clamping nut (8), an insulation cushion (9), anO-shaped ring (10), a wiring terminal clamping nut (12) and a locatingscrew (13).
 2. (canceled)
 3. The cylindrical single-piece lithium-ionbattery of 400 Ah according to claim 1, wherein the aluminum foil has athickness of 30±2 mm, and width of 320±1 mm; and the length of thepositive and negative electrode sheets both have a length of 33.81 m. 4.The cylindrical single-piece lithium-ion battery of 400 Ah according toclaim 23, wherein the tab has a length of 70±1 mm, width of 10±0.1 mm,and thickness of 0.15±0.015 mm.
 5. The cylindrical single-piecelithium-ion battery of 400 Ah according to claim 4, wherein three safetyvalve sheets are provided on each of positive and negative electrodesheets; and each valve sheet has a diameter of 13 mm, thickness of 0.5mm, and burst pressure of 7.5-8 kg.
 6. The cylindrical single-piecelithium-ion battery of 400 Ah according to claim 5, wherein thecylindrical battery enclosure (1) and electrode cover (11) are all madeof stainless steel, and have a diameter of 134 mm, length of 450 mm, andwall thickness of 1 mm.
 7. A method of making a cylindrical single-piecelithium-ion battery of 400 Ah as defined in claim 5, comprising thesteps of: (1) Preparation of electrodes: pre-baked crude materialsincluding LiFePO4, conductive carbon black, graphite, adhesive PVDF, andsolvent NMP in weight % of 42.0-43.01.3-1.7 0.8-1.22.5-3.551.0-53.0 areevenly mixed together to form battery positive electrode slurry;pre-baked crude materials including lithium titanate, conductive carbonblack, graphite, adhesive PVDF, and solvent NMP in weight % of49.0-50.00.8-1.20.8-1.23.0-4.044.0-46.0 are evenly mixed together toform battery negative electrode slurry; during coating and rollingprocess, both of the positive and negative electrodes use aluminum foilas the current-collector; the aluminum foil has a thickness of 30±2 mm,and width of 320±1 mm; the length of both positive and negativeelectrode sheets is 33.81 m; (2) Assembly of the battery: the electrodesheets obtained from above steps are heated for 48 h at a temperature of100; then the positive and negative electrode sheets are placed to bealigned with and parallel with a membrane and are loaded into a fullautomatic winding machine; next, one hundred of aluminum tabs are weldedonto an aluminum foil edge of each positive and negative electrodesheets, and high-temperature resistant adhesive paper is employed tosecure firmly a root portion of the tabs; each aluminum tab of positiveand negative electrode sheets has a length of 70±1 mm, width of 10±0.1mm and thickness of 0.15±0.015 mm; the plurality of evenly dividedpositive and negative tabs (4) pass through a space defined between thewiring terminal (6) and sliding ring (7), and then are locked by the tabclamping nut (8) (this connection manner is called “wiring collar”); acell pack is carefully inserted into the enclosure (1); each of two endsof the enclosure (1) is wrapped by a supporting bracket (5); afterfinishing of the bracket (5), the wiring terminal (6), O-shaped ring(10), insulation cushion (9) and cover (11) are assembled together insequence and are clamped together by the clamping nut (12) and locatingscrew (13); three safety valve sheets are provided on each of positiveand negative electrode covers; each valve sheet has a diameter of 13 mm,thickness of 0.5 mm, and burst pressure of 7.5-8 kg; during winding,assembling and welding procedure, a multimeter is used to detect shortcircuit; when doing so, vacuum injecting means is used to performelectrolyte injection; said electrolyte is LiPF6EC+PC+DMC +DEC; finally,a laser welder runs to weld covers to two ends of the battery in asealing manner.